Electric shielding structures

ABSTRACT

Wireless power transmitting devices according to embodiments of the present technology may include a contact surface configured to support one or more wireless power receiving devices. The wireless power transmitting devices may include a plurality of coils. The wireless power transmitting devices may also include a shield positioned between the plurality of coils and the contact surface. The shield may include one or more shield members, each shield member axially aligned with a separate coil of the plurality of coils, and may include a multilayer structure exhibiting various conductivities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/145,503, filed Sep. 28, 2018, which claims the benefit of U.S.Provisional Application No. 62/688,547, filed Jun. 22, 2018, entitled“ELECTRIC SHIELDING STRUCTURES”, each of which are hereby incorporatedby reference in their entirety for all purposes.

TECHNICAL FIELD

The present technology relates to wireless charging systems. Morespecifically, the present technology relates to shielding structures forwireless charging systems.

BACKGROUND

Wireless charging systems allow power transmission to devices withoutrequiring a power cord or other connective wire coupled to the device tobe powered or recharged. Wireless charging systems, as well as thedevices being charged, may produce noise and emissions that can reducecharging efficiency, and may be subject to regulatory compliance.

SUMMARY

Wireless power transmitting devices according to embodiments of thepresent technology may include a contact surface configured to supportone or more wireless power receiving devices. The wireless powertransmitting devices may include a plurality of coils. The wirelesspower transmitting devices may also include a shield positioned betweenthe plurality of coils and the contact surface. The shield may includeone or more shield members, each shield member axially aligned with aseparate coil of the plurality of coils.

In some embodiments, the shield may include a conductive chassisextending about a perimeter of the shield. The shield may include aconductive sheet spanning an internal area defined by the conductivechassis. The conductive sheet may include a first material, and the oneor more shield members may include a second material. The conductivesheet may be characterized by a higher sheet resistance than the shieldmembers. The shield may include a conductive drain extending from atleast one shield member of the one or more shield members to theconductive chassis. The shield may include a plurality of shieldmembers, and each shield member may be electrically coupled with anothershield member with a bridge or may be electrically coupled with theconductive chassis with a conductive drain.

In some embodiments, the conductive drain may be characterized by anarcuate shape. The conductive drain may be positioned between the atleast one shield member and the conductive chassis, and the conductivedrain may be shaped and positioned to limit overlap with an underlyingcoil relative to a straight-member conductive drain. Each coil of theplurality of coils may be characterized by a substantially annularshape, and each shield member of the one or more shield members mayinclude a body characterized by a substantially annular shape. Eachshield member of the one or more shield members may define a gapextending from an inner annular edge of the body to an outer annularedge of the body, and the gap may form a discontinuity about acircumference of each shield member. Each shield member may furtherdefine a plurality of slots extending from the inner annular edge of thebody towards the outer annular edge of the body. Each shield member ofthe one or more shield members may include a grounding pin extendingfrom an inner annular edge of the body and electrically coupling theshield member with a ground of the wireless power transmitting device.

Some embodiments of the present technology may also encompass a wirelesspower transmitting device. The device may include a contact surfaceconfigured to support one or more wireless power receiving devices. Thedevice may include a first layer of coils distributed in a first planararrangement. The device may include a second layer of coils verticallyoffset from the first layer of coils and positioned between the contactsurface and the first layer of coils. The second layer of coils may bedistributed in a second planar arrangement whereby coils of the secondlayer of coils are laterally offset from coils of the first planararrangement. The device may also include a shield positioned between thesecond layer of coils and the contact surface. The shield may include ashield member overlying and aligned with a coil of the second layer ofcoils.

In some embodiments, the shield may include a conductive chassisextending about a perimeter of the shield. The shield may include aconductive sheet spanning an internal area defined by the conductivechassis. The conductive sheet may include silver, and the shield membermay include copper. The shield may include a plurality of shieldmembers, and each shield member may be electrically coupled with anothershield member with a bridge or may be electrically coupled with theconductive chassis with a conductive drain.

Some embodiments of the present technology may also encompass a wirelesspower transmitting device. The device may include a contact surfaceconfigured to support one or more wireless power receiving devices. Thedevice may include a plurality of coils. The device may also include ashield positioned between the plurality of coils and the contactsurface. The shield may include a conductive chassis, a conductive sheetextending across an internal area defined by the conductive chassis, anda shield member positioned on the conductive sheet and overlying a coilof the plurality of coils.

In some embodiments, the conductive sheet may include a first material,and the shield member may include a second material. The conductivesheet may be characterized by a higher sheet resistance than the shieldmember. The shield may include a plurality of shield members, and eachshield member may be electrically coupled with another shield memberwith a bridge or may be electrically coupled with the conductive chassiswith a conductive drain. Each coil of the plurality of coils may becharacterized by a substantially annular shape, and each shield memberof the plurality of shield members may include a body characterized by asubstantially annular shape. Each shield member of the plurality ofshield members may define a gap extending from an inner annular edge ofthe body to an outer annular edge of the body, and the gap may form adiscontinuity about a circumference of each shield member body.

Such technology may provide numerous benefits over conventionaltechnology. For example, the present systems may reduce device emissionsand electrical noise. Additionally, the systems may reduce eddy currentson shield components and limit an impact on charging efficiency. Theseand other embodiments, along with many of their advantages and features,are described in more detail in conjunction with the below descriptionand attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedembodiments may be realized by reference to the remaining portions ofthe specification and the drawings.

FIG. 1 shows a schematic diagram of a wireless charging system accordingto some embodiments of the present technology.

FIG. 2 shows a schematic plan view of a wireless power transmittingdevice according to some embodiments of the present technology.

FIG. 3A shows a schematic perspective view of a wireless powertransmitting device according to some embodiments of the presenttechnology.

FIG. 3B shows a partial schematic perspective view of a wireless powertransmitting device according to some embodiments of the presenttechnology.

FIG. 4 shows a schematic plan view of an exemplary shield for a wirelesspower transmitting device according to some embodiments of the presenttechnology.

FIGS. 5A-5G show schematic plan views of exemplary shields for awireless power transmitting device according to some embodiments of thepresent technology.

FIG. 6A shows a chart of emissions effects at a first coil position forexemplary shields according to some embodiments of the presenttechnology.

FIG. 6B shows a chart of emissions effects at a second coil position forexemplary shields according to some embodiments of the presenttechnology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include exaggerated material forillustrative purposes.

In the figures, similar components and/or features may have the samenumerical reference label. Further, various components of the same typemay be distinguished by following the reference label by a letter thatdistinguishes among the similar components and/or features. If only thefirst numerical reference label is used in the specification, thedescription is applicable to any one of the similar components and/orfeatures having the same first numerical reference label irrespective ofthe letter suffix.

DETAILED DESCRIPTION

A wireless power system may include a wireless power transmitting devicethat allows power to be transmitted wirelessly to a wireless powerreceiving device. The wireless power transmitting device may be a devicehaving a number of forms including a wireless charging mat, a wirelesscharging puck, a wireless charging stand, a wireless charging table, orother wireless power transmitting equipment. The wireless powertransmitting device may include one or more coils, such as inductioncoils or wound coils, that are used in transmitting wireless power toone or more wireless power receiving coils in wireless power receivingdevices. The wireless power receiving devices may be any number ofrechargeable devices that incorporate an induction coil or coilsconfigured to receive power from the transmitting coil or coils. Anydevice may be configured to receive wireless power, including portabledevices including cellular telephones, electronic watches, wearabledevices including fitness devices, media players, computers includinglaptop computers and tablet computers, battery-powered earphones, remotecontrols, or any other electronic device or other wireless powerreceiving equipment.

During operation, the wireless power transmitting device may supplyalternating current signals to one or more wireless power transmittingcoils. In response, the transmission coils may transmitalternating-current electromagnetic signals, or wireless power signals,to one or more corresponding coils in the wireless power receivingdevice. Rectifier circuitry in the wireless power receiving device mayconvert the received wireless power signals into direct-current (DC)power for powering the wireless power receiving device, or recharging abattery, for example.

An illustrative wireless power system or wireless charging system isshown in FIG. 1. As illustrated, wireless power system 8 may includewireless power transmitting device 12, and one or more wireless powerreceiving devices, such as wireless power receiving device 10. Device 12may be a stand-alone device such as a wireless charging mat, may bebuilt into furniture, or may be other wireless charging equipment.Device 10 may be any portable electronic device including any of thecomponents previously described. During operation of system 8, a usermay place one or more devices 10 on a contact surface of device 12,which may constitute a charging surface. Power transmitting device 12may be coupled with a source of alternating-current voltage such asalternating-current power source 50, such as a wall outlet that suppliesline power or other source of mains electricity or a portable powersource, which may include an additional device such as a laptopcomputer, for example. Power transmitting device 12 may also oralternatively include a battery, such as battery 38, for supplyingpower. A power converter, such as AC-DC power converter 40, can convertpower from a mains power source or other AC power source into DC powerthat may be used to power control circuitry 42 and other circuitry indevice 12. During operation, control circuitry 42 may use wireless powertransmitting circuitry 34 and one or more coils 36, which may beelectrically coupled with circuitry 34, to transmit alternating-currentelectromagnetic signals 48 to device 10, and which may provide wirelesspower to wireless power receiving circuitry 46 of device 10.

Power transmitting circuitry 34 may include switching circuitry, such astransistors in an inverter circuit, which may be engaged or disengagedbased on control signals provided by control circuitry 42 to create ACcurrent signals through appropriate coils 36. As the AC currents passthrough a coil 36 that is being driven by the inverter circuit,alternating-current electromagnetic fields, which may constitutewireless power signals 48, may be produced. The fields may be receivedby one or more corresponding coils 14 coupled with wireless powerreceiving circuitry 46 in receiving device 10. When thealternating-current electromagnetic fields are received by coil 14,corresponding AC currents and voltages may be induced in coil 14.Rectifier circuitry in circuitry 46 may convert received AC signalsassociated with wireless power signals from one or more coils 14 into DCvoltage signals for powering device 10. The DC voltages may be used indirectly powering components in device 10 such as display 52, buttons,components, or other sensors 54, wireless communications circuitry 56,or other input-output devices 22 and/or control circuitry 20. Theconverted voltages may also be used to charge an internal battery indevice 10, such as battery 18.

Devices 12 and 10 include control circuitry 42 and 20, which may includestorage and processing circuitry such as microprocessors,microcontrollers, and/or application-specific integrated circuits withprocessing circuits. Control circuitry 42 and 20 may be configured toexecute instructions for implementing desired control and communicationsfeatures in system 8. For example, control circuitry 42 and/or 20 may beused in determining power transmission levels, processing sensor data,processing user input, processing other information such as informationon wireless coupling efficiency from transmitting circuitry 34,processing information from receiving circuitry 46, using informationfrom circuitry 34 and/or 46, such as signal measurements on outputcircuitry in circuitry 34 and other information from circuitry 34 and/or46, to determine when to start and stop wireless charging operations.The circuitry may be used in adjusting charging parameters such ascharging frequencies, determining coil assignments in a multi-coilarray, measuring wireless power transmission levels, and performingother control functions.

In an exemplary system, wireless transmitting device 12 may be awireless charging mat or other wireless power transmitting equipmentthat may include an array of coils 36 configured to supply wirelesspower over a wireless charging surface. An illustrative arrangement isshown in FIG. 2, where device 12 includes an array of coils 36 that maybe used in wireless charging operations as previously explained.Wireless transmitting device 12 may include an overlying contact surface60 configured to detect when a wireless power receiving device is placedon the contact surface. For example, sensors or other devices may detectthe presence of a device having wireless power receiving capabilities.

Coils 36 are illustrated in an exemplary pattern in which multiplelayers of coils are distributed in a stacked arrangement within device12. In other embodiments similarly encompassed by the present technologymore or fewer coils may be included in the wireless transmitting device12 including 1 coil or 2 or more coils, including greater than or about5 coils, greater than or about 10 coils, greater than or about 15 coils,greater than or about 20 coils, greater than or about 50 coils, greaterthan or about 100 coils, greater than or about 1,000 coils, or moredepending on the size, shape, and patterning of the coils 36, as well asthe size and shape of wireless power transmitting device 12. Forexample, in some embodiments, device 12 may be the size of a placemat orsmaller, while in other embodiments device 12 may be a conference tablehaving dimensions of several meters. Coils 36 may be distributed in anypattern and may be arranged in any number of configurations includingany number of layers. In embodiments encompassed by the presenttechnology the coils may be all of a similar size and shape asillustrated, although in other embodiments coils of different sizes andshapes may be used together within a device. In some embodiments, coils36 may be arranged in a single row, two rows, three rows, five rows, ormore, depending on the distribution of coils. For example, coils 36 maybe arranged in each row so as not to completely overlap a coil in anyother row. As illustrated, although coils 36 overlap underlying coils,there is a lateral offset between the coils in each row, as well as inall rows. This offset may both increase an area for charging coverageacross the contact surface 60, as well as limit or reduce detrimental orinterference effects on proximate coils. Coils 36 may not be exposed insome embodiments, and may be enclosed or covered by a planar dielectricstructure such as a plastic member, or other material or structure,forming contact surface 60.

During operation, a user may place one or more devices 10 on contactsurface 60, which may be configured to support one or more wirelesspower receiving devices. Foreign objects such as coins, paper clips,scraps of metal foil, and/or other foreign conductive objects may beaccidentally placed on surface 60. System 8 may be configured toautomatically detect whether conductive objects located on surface 60correspond to devices 10 or incompatible foreign objects, and mayrespond in each case appropriately, such as by engaging coils proximateto devices 10, while disengaging or not engaging coils proximateincompatible foreign objects. For example, external objects 62 and 64may overlap one or more coils 36. In some embodiments, objects 62 and 64may each be portable electronic devices 10, and system 8 may engage oneor more coils proximate or underlying the devices. In other situations,either object 62 or 64 may be an incompatible object, and system 8 maynot engage, or may actively disengage coils proximate or underlying thedevices. In some embodiments, before system 8 allows wireless power tobe transmitted to some objects, system 8 may check whether objectslocated on surface 60 include sensitive components such asradio-frequency identification (RFID) devices or other potentiallysensitive electronic equipment that could be damaged upon exposure tofields from coils 36. System 8 may engage coils at reduced power in suchsituations, or may not engage coils proximate sensitive devices.

Wireless charging systems may generally operate on magnetic fields.However, the components of both the wireless power transmission deviceand the wireless power receiving device may include other electricalcomponents and conductive components, which may produce or enhanceradiative emissions and conductive emissions that interfere withcharging and other operations. Electric noise generated by components orby specific characteristics of the transmitting or receiving devices maybe capacitively coupled to the adjacent device, which may result infurther enhancement of the emissions. An electric field shield, ore-shield or shield as will be described throughout the disclosure, maybe positioned between the coils of the transmitting and receivingdevices. In the simplest sense, a conductive sheet may be positionedacross the surface of the transmitter to block noise or unwantedemissions, but such a sheet would simultaneously block the chargingprocess. To avoid drastic reductions in charging efficiency, a solide-shield may be limited to lower conductivity components and/or minimalthicknesses. However, these concessions may adversely limit theoperation on emissions. Slots or cuts may be formed in a solid shield,but in multiple-coil arrangements introducing slots may increaseunwanted eddy currents that act back upon the magnetic field and furtheraffect charging efficiency. Accordingly, electric field shields formultiple-coil charging systems face many competing challenges.

The present technology may include a shield, or e-shield, utilizing oneor more components configured to reduce electric field strengths oncoils characterized by higher emissions, while limiting an impact onmagnetic fields. Returning to FIG. 2, an exemplary wireless powertransmitting device 12 may include multiple layers of coils, or simplymultiple closely spaced coils. Each coil of the multiple coils orplurality of coils may produce different electric fields based on anumber of factors. For example, coils nearer to an edge of the devicemay be subject to a more asymmetrical ground plane, while coils nearerto a center of the device may have a more symmetrical ground plane.Exemplary devices may include a ferrite layer beneath the coils, whichmay also affect coils in a non-uniform manner depending on the thicknessand shape of the ferrite. Additionally, each coil may be characterizedby a different rotation of the coil, as well as different terminationconfigurations in whether the terminations are co-located or positionedon separate sides of the coil. Wireless power transmitting device 12 mayalso include a cable 65, which may couple with power source 50 describedpreviously, and may couple with device 12 at connector 67. Each coil maybe distributed at a distance from connector 67, which may further impactelectrical characteristics. For example, while one coil may be proximateconnector 67, another coil may be twice the distance to connector 67,which may impact the emissions at certain frequencies. Consequently,many characteristics of the device 12 and associated components mayimpact the electrical emissions.

In some embodiments having layers of coils, coils adjacent the contactsurface may have increased emissions over coils beneath the top layer.For example, FIG. 2 illustrates a configuration including three layersof coils, although fewer or more layers may be included. A first layerof coils 35 may be seated closest to a ferrite or other material layer,when included, and may be furthest from contact surface 60. First layerof coils 35 is illustrated as having six coils in a first arrangementacross a first plane, although more or less coils as well as any otherlateral distribution across the first plane is similarly encompassed,such as seven coils, eight coils, or more. A second layer of coils 37may be included on a second plane vertically offset from, such as above,the first plane. The second coils may be distributed in a secondarrangement, which may be similar to or different from the arrangementof the first layer of coils. As illustrated, the second layer of coilsincludes seven coils across a second plane, although more or less coilsas well as any other lateral distribution across the second plane issimilarly encompassed. The coils of the second layer of coils may belaterally offset from coils in the arrangement of the first layer ofcoils. Hence, in some embodiments no coils or few coils of the secondlayer of coils may fully overlap any coil of the first layer of coils.

The illustrated embodiment also includes a third layer of coils 39overlying the second layer of coils 37. The third layer of coils may beclosest to the contact surface 60. The third layer of coils may beincluded on a third plane vertically offset from, such as above thesecond plane and/or first plane. The third coils may be distributed in athird arrangement, which may be similar to or different from thearrangement of the first or second layers of coils. As illustrated, thethird layer of coils includes seven coils across a third plane in asimilar arrangement as the second layer of coils, although more or lesscoils as well as any other lateral distribution across the third planeis similarly encompassed. The third layer of coils may be laterallyoffset from coils in the first and second layers, and in someembodiments no coils or few coils of the third layer of coils may fullyoverlap any coil of the first layer and/or second layer of coils. Asseen in the example illustrated, upper coils, such as those in thesecond and third layers of coils, may act as a partial shield tounderlying coils, which may reduce the emissions of the underlyingcoils. However, the uppermost coils in the third layer of coils, withoutan additional shield, may not be affected by underlying components, andmay generate higher emissions than coils in the second layer and firstlayer.

In some embodiments of the present technology, a shield may be includedthat may selectively target coils predetermined to contribute higherlevels of emissions, or may contribute emissions at particularfrequencies to be controlled. Whether from a lateral position within thedevice configuration, or from additional characteristics such as aposition in an uppermost layer, for example, individual coils may beselectively targeted with e-shields according to the embodiments of thepresent technology.

FIG. 3A shows a schematic perspective view of a wireless powertransmitting device 300 according to some embodiments of the presenttechnology. Wireless power transmitting device 300 may include any ofthe components of wireless power charging device 12 described above, andmay include any of the components and arrangements previously described.Device 300 may include a housing 305 incorporating a number ofcomponents for providing wireless power to one or more receivingdevices. In some embodiments housing 305 may be or include a shell orcasing in which the components may be contained, and may be of anynumber of form factors. For example, housing 305 may be a mat, plate,puck, or other similarly sized component, although in other embodimentshousing 305 may be a table, countertop, nightstand, desk, or any surfacewithin which additional components for providing wireless power may becontained.

Housing 305 may be made of any number of materials including plastics,woods, metals, stones, or any material that may be formed, carved, orhollowed to allow placement of additional components. Housing 305 mayinclude a contact surface 307, which may be a dielectric material or anyother material that may be configured to support one or more wirelesspower receiving devices. For example, in some embodiments a contactsurface 307 extending across a top area of the housing may be aconductive material, although in some embodiments the choice ofconductive material may be configured to limit blocking of orinterference with magnetic or other radiated waves through the contactsurface, which may provide wireless charging capabilities.

Within housing 305 may be a number of components including circuitry,which may include a circuit board, sensors for detecting objects on orproximate contact surface 307 and for measuring or controlling theprovision of wireless power from device 300, as well as any othermaterials as previously described. Housing 305 may include material 315,which may be ferrite in one example, or any other material that may beused to block, direct, or otherwise contribute to control of generatedwireless power fields. Above material 315 may be one or more coils 310,such as a plurality of coils, which may be or include characteristics ofcoils 36 described above, and may be used to contribute to thegeneration of wireless power, which may be transmitted to a receivingdevice positioned on contact surface 307. Coils 310 may include anynumber of coils that may be distributed and arranged in any patternacross an internal volume of device 300. The coils may be included in asingle layer, or may be included in multiple layers, including greaterthan or about 2 layers, greater than or about 3 layers, greater than orabout 4 layers, greater than or about 5 layers, greater than or about 10layers, or more. Device 300 may also include a connector 320, which mayallow a power source to be coupled with wireless power transmittingdevice 300, and may operate as an electrical ground path from thedevice.

Wireless power transmitting device 300 may also include a shield 325positioned between coils 310 and contact surface 307. Shield 325 mayinclude one or more shield members 330 that may be distributed acrosscoils 310. Shield members 330 may be stand-alone components asillustrated, and thus shield 325 may include multiple separatecomponents, although as will be described further below in additionalembodiments shield 325 may include a one-piece design of the componentsor shield members. Shield members 330 may be positioned to affectelectric noise from one or more of the coils 310. As previouslyexplained, based on a number of factors, certain coils may contribute toelectric noise generation more than other coils. Operational testing ofa particular device 300 form factor may identify one or more coilscontributing higher emissions. For example, in configurations includingmultiple layers of coils, a top layer of coils may be contributinghigher emissions than lower layers of coils. Shield members 330 may bepositioned in a configuration related to the coils contributing toincreased radiative or conductive emissions.

As shown in the figure, shield members 330 may be positioned over one ormore coils, and may be positioned to substantially overlap individualcoils. In one embodiment shown in FIG. 3A, shield members 330 arearranged in a layer to distribute one shield member 330 over each coil310 in a top layer of coils, such as all seven coils as described in toplayer of coils 39 of FIG. 2. It is to be understood that when more orfewer coils are included, more or fewer shield members may be includedas well. Additionally, shield members 330 may not be positioned overevery coil within a particular coil layer. Because shield members 330may impact charging efficiency, the number of shield members may beselected to beneficially reduce electrical noise, while minimizing animpact on charging. Shield members 330 may be axially aligned withindividual coils 310, and may be sized to be of a smaller diameter,substantially similar diameter, or greater diameter than a coil 310 overwhich the shield member 330 is positioned.

Turning to FIG. 3B is shown a partial schematic perspective view ofwireless power transmitting device 300 according to some embodiments ofthe present technology. FIG. 3B may show an enhanced view of shield 325and shield members 330. The coils of wireless power transmitting device300 may include wound coils that may each be characterized by asubstantially annular shape, which may allow one or more wireconnections within a central area defined by the annulus. Although theshields may be characterized by any shape, including an elliptical orother geometric pattern, in some embodiments shield members 330 may alsobe characterized by a substantially annular shape. Such a shape maycorrespond to the annular shape of the coil over which the shield memberis being positioned, while limiting effects on additional coils, whichmay be present in lower layers of coils. For example, when a solidshield member is utilized, the shield member may overlap the intendedcoil, and may also cover more than only the overlapping portion ofunderlying coils, and may also cover underlying coil portions positionedunder a central area defined by an overlying coil. When covered by ashield, the shield may further limit wireless charging fieldtransmission for the underlying coil or coils, which may further reducecharging efficiency of the wireless power transmitting device.Accordingly, in some embodiments shield members 330 may be characterizedby an annular shape to limit impact on underlying coils separate fromthe coil with which the shield member is associated.

Shield members 330 may define a gap 335 formed radially across or insome configuration through each shield member 330, as will be describedin further detail below. Gap 335 may fully extend from an inner annularedge of the shield member 330 to an outer annular edge of the shieldmember, which may form a discontinuity about a circumference of eachshield member. In embodiments where shield member 330 may becharacterized by a non-circular or elliptical geometry, a gap may beformed as a discontinuity about a perimeter of the shield member, whichmay also be termed a circumference. Shield members 330 may be aconductive material in some embodiments to allow blocking of electricalnoise. However, such a conductor proximate a source coil may allow eddycurrents to be induced on the shield members 330 from developed magneticfields from the underlying coils. If the shield member forms a completecircular shape, or forming a complete loop, the developed eddy currentsmay increasingly react back on the coil opposing the magnetic field andfurther reducing charging efficiency of the device. Accordingly, gap 335may reduce or limit eddy current generation as well as the accompanyingheat generation from the eddy currents.

Shield members 330 may include a grounding pin 340, or grounding memberallowing dissipation of generated electrical currents on the shieldmembers 330. Grounding pin 340 may extend from either the inner annularedge or the outer annular edge of the shield members 330. Asillustrated, in some embodiments the grounding pin 340 extends from aninner annular edge of the shield member. Grounding pin 340 mayelectrically couple the shield member with an electrical ground of thewireless power transmitting device 300. For example, shield members 330may be at an uppermost layer within the housing of the wireless powertransmitting device, and may be located just below a contact surface ofthe housing. A ground within the housing may be located at a lower planewithin the housing, including on an underlying circuit board, and may belocated below all coil layers, below a ferrite or other material layer,or elsewhere. Grounding pin 340 may be adapted to extend from an innerannular edge of each shield member and extend laterally to or towards acentral region defined by the shield member. The grounding pin 340 maythen transition vertically and extend down or otherwise verticallywithin the housing to electrically connect or couple with an electricalground within the device. In other embodiments, the grounding pin 340may extend laterally to an edge or other location to couple with thehousing, which may provide a ground path. Additionally, in someembodiments, grounding pins 340 may extend to one or more other shieldmembers to electrically couple the shields, which may then include oneor more ground paths from one or more other shield members to thehousing laterally, vertically, or otherwise, which may be similar to anyof the additional embodiments described elsewhere.

Shield members 330 may be or include a conductive material, which mayfacilitate a reduction in electrical noise. The shield members mayinclude any number of materials or combinations of materials, which maybe or include silver, copper, aluminum, zinc, nickel, stainless steel,or any other material which may be used to reduce the electrical noisetransmitted or formed within the wireless power transmitting device.

Additional shield designs are also encompassed in the presenttechnology, which may further control radiative and conductive emissionsfrom or to the wireless power transmitting device. As explainedpreviously, coils in lower layers of coils may also produce emissions,although these emissions may be less than those in upper layers ofcoils, or coils in a similar plane, which may be characterized by higheremissions due to other factors described above. These emissions may bereduced or controlled in some embodiments by utilizing a compound ormulti-layer e-shield that may address coils generating lower levels ofemissions due to their lateral location or position in a lower layer ofcoils. The multi-layer or multi-material e-shields may further controlnoise associated with wireless charging operations.

FIG. 4 shows a schematic plan view of an exemplary shield 400 for awireless power transmitting device according to some embodiments of thepresent technology. Shield 400 may be a multi-layer or multi-materialshield providing additional reduction in electrical noise by providing alow-level reduction to all coils included within a device, as well asproviding a targeted reduction in individual coils contributingincreased emissions. Shield 400 may be utilized with any of the wirelesspower transmitting devices previously described, and may be positionedwithin a device housing as an internal component. The shield 400 may bepositioned proximate a contact surface of the wireless power receivingdevice, and may be positioned between a contact surface and a pluralityof coils used for wireless power charging. Any device with which shield400 may be used may include any number, configuration, or arrangement ofcoils, including coils of different sizes, shapes, orientations, andlayers.

Shield 400 may include a number of shield members 410 disposed withinthe shield 400. Shield members 410 may include any of the patterns,materials, or characteristics as shield members 330 describedpreviously. Shield members 410 may be positioned with the shield 400such that when shield 400 is incorporated within a wireless powertransmitting device, shield members 410 are axially aligned or otherwiseassociated with or overlie particular coils of the device. Shield 400 isillustrated with seven shield members 410 distributed in a similarorientation as described previously relative to the seven coils of thetop layer of coils 39 included in that exemplary device. However, it isto be understood that shield 400 may include any number of shieldmembers which may be used or positioned within the shield to selectivelyoverlie particular coils determined to generate electrical noise in anyconfiguration of coils. The remaining portions of the disclosure willsimilarly be based on the coil configuration illustrated in FIG. 2,although it is to be understood that any number of additional oralternative configurations as described previously may similarly benefitfrom incorporation of a shield 400, or variation thereof as discussedelsewhere.

Shield 400 may include a chassis 415 that may be made of any material,and may include a conductive material. For example, chassis 415 may beor include any of the previously identified materials, or any otherconductive material, which may allow electrical current to bedistributed about the chassis. In some embodiments, chassis 415 may bethe same material as shield members 410. Chassis 415 may becharacterized by any number of designs, and may extend about a perimeterof the shield. Chassis 415 may be sized according to the size of thecorresponding wireless power transmitting device in which shield 400 maybe incorporated. Chassis 415 may be sized to couple or connect with ahousing of the device, which may be any of the housing materialspreviously described. Chassis 415 may define a coupling location 417,which may allow transfer of electrical current to an electrical groundof the device, including through a cable coupled with the device aspreviously described. Coupling location 417 may be a pattern or profileallowing overlap of conductive chassis 415 with a conductive aspect ofan associated housing, which may allow transfer of current from theshield 400.

The profile of chassis 415 may form an elliptical, polygonal, or othergeometric structure, which may form a loop of conductive material. Tolimit eddy currents induced on the conductive chassis 415, the chassismay define a number of contact tips 416 distributed about the chassis.As illustrated, contact tips 416 are formed from an outer edge of thechassis towards an inner edge, such as an inner annular edge, which mayform a continuous edge about the structure. In other embodiments, thechassis may be characterized by the reverse profile in which an outeredge of the chassis forms a continuous edge, while contact tips 416 areformed from the inner edge towards the outer edge. Any number of contacttips may be formed about the chassis, and the number may depend on thesize of the shield and/or the extent of impact on charging operations.For example, a shield characterized by a diameter of 50 cm or less, maydefine up to or at least 50 contact tips, while a shield characterizedby a diameter of 5 meters, less, or more, may define less than 300contact tips. In other embodiments a shield characterized by a diameterof 5 meters may define at least 1,000 contact tips in otherconfigurations. Any number of contact tips may be formed, which mayfacilitate a reduction in eddy current effects on the chargingcapabilities of the wireless power transmitting device.

Shield 400 may also include a sheet 420 spanning an internal areadefined by the chassis 415. Sheet 420 may further facilitate a reductionin electrical noise. Shield members 410 may be formed over or under thesheet 420, and in some embodiments sheet 420 may be formed about shieldmembers 410 so that sheet 420 and shield members 410 are coplanar alonga plane defined by sheet 420. Sheet 420 may be or include any of theconductive materials previously described. The conductivity of sheet 420may be tuned to limit an impact on the charging capabilities of theassociated wireless power transmitting device. For example, byincreasing a thickness of sheet 420 or selecting a more conductivematerial, sheet 420 may further reduce emissions. However, as thicknessand/or conductivity increases across sheet 420, device chargingcapability may be reduced, and may be limited. Accordingly, in someembodiments sheet 420 may be sized and selected to be characterized by alower conductivity than shield members 410 positioned across sheet 420.

For example, sheet 420 may include a thin-film conductive material,which may be characterized by a thickness of less than or about 1 μm,and may be characterized by a thickness of less than or about 500 nm,less than or about 250 nm, less than or about 100 nm, less than or about90 nm, less than or about 80 nm, less than or about 70 nm, less than orabout 60 nm, less than or about 50 nm, less than or about 40 nm, lessthan or about 30 nm, less than or about 20 nm, less than or about 10 nm,or less, as well as within any lesser range encompassed by these statedranges. By forming sheet 420 at a reduced thickness, sheet 420 may be orinclude a more conductive material. For example, in some embodimentsshield members may be or include copper, while sheet 420 may be orinclude silver. Although silver may be more conductive than copper, thethickness of sheet 420 may be such that sheet 420 is characterized by asheet resistance higher than the shield members 410. Shield members 410may be characterized by a thickness between or about 100 nm and about100 μm, such as greater than or about 1 μm, greater than or about 10 μm,greater than or about 20 μm, greater than or about 30 μm, greater thanor about 40 μm, greater than or about 50 μm, greater than or about 60μm, greater than or about 70 μm, greater than or about 80 μm, greaterthan or about 90 μm, greater than or about 100 μm, or more.Consequently, the sheet resistance of shield members 410 may be lowerthan the sheet resistance of sheet 420. Because shield members 410 maybe sized to specific coil sizes, the increased conductivity mayfacilitate reductions in electrical noise, while limiting reductions inmagnetic fields or other mechanisms for wireless charging.

Shield members 410 may include a body 412 and an appendage 414 from eachshield member body 412. In the illustrated embodiment, appendage 414 mayconstitute a conductive drain extending from the shield member body 412,which may be similar to the grounding pin previously described. Theappendage 414 may also be a bridge as will be described further below.Body 412 of each shield member 410 may be sized and shaped to overlap anunderlying coil, and may be positioned when shield 400 is coupled with awireless power transmitting device to be axially aligned with anunderlying coil of the device as previously described. Body 412 mayinclude a gap 411 as discussed above, which may be formed from an innerannular edge through an outer annular edge of the shield member body,and which may form a discontinuity about a circumference or perimeter ofthe shield member to reduce an impact of eddy currents on the underlyingcoils. The location of the gap may affect electrical fields, and in someembodiments the shield members may be formed or positioned withconsideration of the gap location of other shield members in the shield.For example, in some embodiments at least two shield members 410 may bearranged so that a gap formed in each respective body 412 may face a gapin the other shield member, which may be an adjacent shield member.Hence, as illustrated, in some embodiments, shield members 410 a and 410b may be incorporated within shield 400 so that the gap in theassociated body of shield member 410 a may face or be in line with thegap in the associated body of shield member 410 b.

Shield 400 may include at least one conductive drain extending from atleast one shield member 410 to the conductive chassis 415. Asillustrated, each appendage 414 shown in FIG. 4 forms a conductive drainextending from the body 412 of each shield member 410 to the chassis415, and/or another ground source, which may include an underlyingcircuit board, for example. Each appendage may be any of the previouslydescribed conductive materials, and in some embodiments may be the samematerial as the shield member bodies. The location and formation of thedrains may also affect emissions in different device configurations, andthe conductive drains may overlap underlying coils, which may furtherimpact charging efficiency of the associated device. For example, insome embodiments the chassis 415 may distribute current to coupling 417,where current may be delivered from the shield 400 to an associatedwireless power transmitting device, and in some embodiments from adevice to ground. The distance of travel from each shield may impact theeffect on emissions. Accordingly, in some embodiments, additionalappendage structures on the shields may be used to limit the length ofdistribution paths, which may improve emission reduction and/or effectson the wireless charging efficiency of the associated device.

FIGS. 5A-5F show schematic plan views of exemplary shields for awireless power transmitting device according to some embodiments of thepresent technology. The illustrations may include variations on theshield structure of FIG. 4, and may include some or all of thecomponents as discussed with FIG. 4. Although some of the illustrationsdo include a chassis, it is to be understood that a chassis may beincluded to distribute current as previously described, and the figuresare more focused on variations in the shield member and appendagestructures of the particular shield members. Any of the shieldsdescribed below may include any of the materials or components describedelsewhere, and may be incorporated with any of the wireless powertransmitting devices described. Additionally, any of the specificallyillustrated variations may be used in combination with other variations,coil or shield member arrangements, or any wireless power transmittingdevices described elsewhere.

FIG. 5A illustrates a variation in the shield members in which oneappendage 505 is a conductive drain extending from the body of theassociated shield member to a conductive chassis and/or other ground orcurrent distribution path, such as an underlying circuit board, forexample. Each of the other appendages forms a bridge between the bodiesof two shield members. As shown, appendage 510, as well as each otherappendage but appendage 505, includes a short trace of materialextending from the body of one shield member to the body of an adjacentshield member. FIG. 5A shows a single arrangement with bridges, and itis to be understood that any other organization of bridges is similarlyencompassed where each shield member body is coupled with another shieldmember body.

Although utilizing bridges and a single drain may reduce the amount ofmaterial, and may reduce some of the conductive paths, such aconfiguration may also have a corresponding impact on operationalefficiency. For example, as previously described, an associated wirelesspower transmitting device in which the shield configuration illustratedmay be used may operate to charge multiple devices, such as a devicepositioned on opposite longitudinal sides of the transmitting device. Insuch a scenario, a coil underlying shield body 520 a, and a coilunderlying shield body 520 b may be selectively engaged. In theconfiguration of FIG. 5A, all current may be delivered from a singlepath through the drain of appendage 505. Consequently, emissionscollected on shield body 520 a and emissions collected on shield body520 b may all flow towards one another and through appendage 505.However, depending on the devices being charged simultaneously, thenoise from one charging may have some contributing effect on the noisefrom the other device. In some beneficial scenarios, these noisecomponents may destructively cancel out, although in other scenariossome amount of constructive development may occur, which may furtherincrease the generated noise, and reduce operating efficiency.

Consequently, including a combination of appendage configurationsincluding some number of drains, and some number of bridges may improvethese effects to accommodate a wider variety of operating conditions.FIG. 5B illustrates one possible scenario in which the same shieldmember body configuration may include an alternate appendage design. Asillustrated, each shield member is electrically coupled with anothershield member with a bridge, and/or is electrically coupled to anexternal edge of the shield, such as to a conductive chassis, with aconductive drain. This may improve the effects produced by multipledevices being charged simultaneously. As shown, the drains may bepositioned towards a side of the shield, such as a side along which aground connection may be made to an associated device as previouslyexplained, although the drains may also be coupled with the chassis inany other location about the structure.

FIG. 5B also illustrates a shield body configuration in which someshield bodies may be positioned similar to an adjacent and inline shieldbody, and thus the gaps may be located at corresponding positionsrelative to the shield. For example, shield body 520 c and shield body520 d may be positioned in line in a similar orientation. Accordingly,gap 522 c of shield body 520 c may be facing in a similar direction asthe gap 522 d of shield body 520 d. FIGS. 4, 5A, and 5B illustrate somecombinations for inline shield bodies in which the gaps are positionedfacing one another, facing in opposite directions from one another, andfacing in a similar direction, respectively. Any combination of theseconfigurations may be used for different shield body pairs, ormultiples, which may provide different effects on emissions.

FIG. 5C illustrates a configuration in which a plurality of slots 530are formed on the shield body. As explained previously, eddy currentsmay be induced on shields of the present technology. Although a gapformed along the shield body may reduce eddy currents, in someembodiments currents may still be circulating on the shield body due tothe lengths or areas of the shield bodies. By forming a number of slots530 on the shield body, eddy currents may be reduced even further byintroducing a more complicated path about the shield. Slots 530 areshown as being defined by the shield bodies from an inner annular edgeof the shield body towards an outer annular edge of the shield body,although the slots may also be formed from the outer annular edge of theshield body towards the inner annular edge of the shield body, as wellas some combination of slots extending inward and outward in otherembodiments.

Unlike a gap formed in each shield body, such as gap 522 e, slots 530may not fully extend to the outer radial edge of the shield body. Eachshield body may define any number of slots, which may be based on thesize of the shield member body, although exemplary configurations mayinclude greater than or about 10 slots, greater than or about 50 slots,greater than or about 100 slots, greater than or about 500 slots, ormore. FIG. 5C illustrates a similar arrangement of appendages as FIG.5A, although it is to be understood that any shield member configurationmay incorporate slots 530, including any variation illustrated,including shield members illustrated in FIG. 3A, as well as anyvariation not expressly illustrated but encompassed by the presenttechnology as an adjustment to any of the illustrated variations.

FIG. 5D illustrates another variation in which not all coils of the toplayer of coils in a layered configuration may include an associatedshield member. Such a configuration may also be applied in any planararrangement of coils as well, and is not intended to be limited tolayered configurations. Depending on the wireless power transmittingdevice size, power, or configuration, few coils may produce emissions tobe controlled. In these scenarios, a shield, which may include any ofthe characteristics of other described shields, may include shieldmembers that may cover only a portion of the coils. For example, coil501 of the illustrated device may not contribute emissions to beaddressed by a shield, or may contribute emissions at a level that maybe addressed by a sheet, such as sheet 420 of an associated shield. Theassociated shield may then include shield members over coils generatinggreater emissions, such as a coil under shield member body 520 f, forexample. Any number of variations on this design may be utilizeddepending on the specific characteristics of a device and the particularcoils generating emissions to be addressed. Additionally, FIG. 5D doesnot illustrate a sheet, such as sheet 420, to allow viewing of coils ina device with which the shield is coupled. It is to be understood thatthe technology also encompasses incorporation of a sheet and chassis, aswell as any other component previously described.

FIGS. 5E and 5F illustrate variations on particular appendage designs,and may be used in combination with any of the arrangements describedelsewhere. For example, FIG. 5E illustrates an embodiment in whichappendage 535 does not connect perpendicularly with chassis 537, but isangled towards a coupling where current may be delivered from theshield. Angling appendages may reduce path lengths, which maybeneficially reduce emissions characteristics. Angling some or allappendages may additionally provide routes of conductive material toavoid underlying coil positions. For example, the angle of appendage535, or any other appendage, may be selected to reduce the overlap withunderlying coils that are not the target of the particular shield body.FIG. 5F shows an additional design that may limit overlap with otherunderlying coils by utilizing an arcuate appendage 540. Appendage 540may be characterized by an arcuate shape that extends from a shield bodyto the chassis, or another appendage or shield body. The particularshape may be selected to limit overlap with an underlying coil, whichmay be less than if a straight-member conductive drain or bridge wasutilized instead. The arcuate appendage may increase path length in someconfigurations, which may be balanced against the benefit of reducingoverlap, to provide the most benefit at the system level for reducingemissions.

FIG. 5G shows an additional shield configuration that may beincorporated in any of the previously discussed designs. Shield member520 g illustrates a gap 522 f configuration in which the gap may notextend in a linear direction radially across the shield member, althoughstill extending radially through the entire shield member. Any number ofconfigurations may be incorporated in various embodiments in which thegap may be formed or a section may be removed from a shield member in anumber of ways. The gap may be formed to accommodate underlyingcomponents, or may be formed to provide particular performancecharacteristics, structural designs, or to facilitate placement in avariety of devices. Accordingly, in some embodiments the gap may beformed radially through a shield member, and may extend linearly, in astepped or angular pattern, in an arcuate configuration as illustrated,or in any other manner to form a continuous break through the shieldmember.

By incorporating shields according to the present technology, emissionsmay be reduced or shifted from certain frequencies. For example, byincorporating shields according to the present technology, resonanceassociated with the coils may be shifted to a lower frequency. Byshifting the resonant frequency of magnetic resonance emissions,emissions occurring at frequencies associated with specificfunctionalities, such as object detection on the transmission device,may be shifted to a lower frequency where the excitation may be reduced.For example, some devices may perform object detection on thetransmission device at frequency ranges below 30 MHz, for example, suchas between about 20 MHz and about 30 MHz, or between about 25 MHz andabout 30 MHz. Accordingly, any particular functionality of thetransmission device that may be occurring within these frequency ranges,may be impacted or impeded by resonance occurring from the magneticfield. However, by incorporating shield members over the coils may shiftthe resonance out of the operating states of the device, which may limitexciting the frequencies and impacting device operations.

FIGS. 6A and 6B show charts of emissions effects at a first coilposition and a second coil position for exemplary shields according tosome embodiments of the present technology. For example, FIG. 6A mayillustrate the effects of various designs on a first coil in a top layerof coils on one side of the wireless power transmitting device, and FIG.6B may illustrate the effects of various designs on a second coil in atop layer of coils on the opposite side of the wireless powertransmitting device. Line 605 shows the magnitude of the emissions ofthe first coil at different frequencies without any shield incorporated,and line 625 shows the magnitude of the emissions of the second coil atdifferent frequencies without any shield incorporated.

Line 610 shows the magnitude of emissions of the first coil at differentfrequencies utilizing a shield structure similar to the configurationillustrated in FIG. 4. As shown, the emissions at 30 MHz has beengreatly reduced, and may limit issues with device operation. Theemissions at 25 MHz has been partly reduced, although such a reductionmay be sufficient for operations performed closer to 30 MHz. Line 640illustrates the magnitude of emissions of the second coil at differentfrequencies utilizing the shield structure similar to the configurationillustrated in FIG. 4. As shown, this shield configuration outperformedother shield structures at the second coil.

Line 620 shows the magnitude of emissions of the first coil at differentfrequencies utilizing a shield structure similar to the configurationillustrated in FIG. 5A. As shown, the emissions at 30 MHz and 25 MHZ hasbeen greatly reduced, and the configuration outperformed other shieldstructures at the first coil. Line 630 illustrates the magnitude ofemissions of the second coil at different frequencies utilizing theshield structure similar to the configuration illustrated in FIG. 5A. Asshown, this shield configuration reduced emissions at each frequency,although the extent of reduction was less than other shield structures,and overall, the performance of the shield structure may not improve onother configurations.

Line 615 shows the magnitude of emissions of the first coil at differentfrequencies utilizing a shield structure similar to the configurationillustrated in FIG. 5B. As shown, the emissions have been reduced at allfrequencies, and is an improvement over the configuration of FIG. 4 atlower frequencies, although not at 30 MHz. Line 635 illustrates themagnitude of emissions of the second coil at different frequenciesutilizing the shield structure similar to the configuration illustratedin FIG. 5B. As shown, this shield configuration reduced emissions ateach frequency, and is an improvement over the configuration of FIG. 5Aat most frequencies, although comparable closer to 30 MHz.

The charts of FIGS. 6A and 6B are intended to illustrate that althoughcertain configurations and appendage designs may improve performance atcertain coil locations, alternative designs may provide more benefit atother coil locations. Accordingly, depending on device operationfrequencies, coil configurations, and shield appendage configurations,an overall profile may be developed for devices to provide emissionsreductions at a system level that affords an amount of benefit forperformance against different emission requirements, and to accommodatedifferent requirements, different configurations or modifications may beincorporated. By utilizing shields according to the present technology,field emissions of wireless power transmitting devices may be reducedand device performance and efficiency may be improved.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included. Where multiple values areprovided in a list, any range encompassing or based on any of thosevalues is similarly specifically disclosed.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a material” includes aplurality of such materials, and reference to “the coil” includesreference to one or more cells and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

What is claimed is:
 1. A wireless power transmitting device, comprising:a contact surface configured to support one or more wireless powerreceiving devices; one or more coils; and a shield positioned betweenthe one or more coils and the contact surface, wherein the shieldcomprises one or more shield members, each shield member axially alignedwith a separate coil of the one or more coils.
 2. The wireless powertransmitting device of claim 1, wherein the shield comprises aconductive chassis extending about a perimeter of the shield.
 3. Thewireless power transmitting device of claim 2, wherein the shieldcomprises a conductive sheet spanning an internal area defined by theconductive chassis.
 4. The wireless power transmitting device of claim3, wherein the conductive sheet comprises a first material, wherein theone or more shield members comprise a second material, and wherein theconductive sheet is characterized by a higher sheet resistance than theshield members.
 5. The wireless power transmitting device of claim 2,wherein the shield comprises a conductive drain extending from at leastone shield member of the one or more shield members to the conductivechassis.
 6. The wireless power transmitting device of claim 5, whereinthe shield comprises a plurality of shield members, and wherein eachshield member is electrically coupled with another shield member with abridge or is electrically coupled with the conductive chassis with aconductive drain.
 7. The wireless power transmitting device of claim 5,wherein the conductive drain is characterized by an arcuate shape,wherein the conductive drain is positioned between the at least oneshield member and the conductive chassis, and wherein the conductivedrain is shaped and positioned to limit overlap with an underlying coilrelative to a straight-member conductive drain.
 8. The wireless powertransmitting device of claim 1, wherein each coil of the one or more ischaracterized by a substantially annular shape, and wherein each shieldmember of the one or more shield members comprises a body characterizedby a substantially annular shape.
 9. The wireless power transmittingdevice of claim 8, wherein each shield member of the one or more shieldmembers defines a gap extending from an inner annular edge of the bodyto an outer annular edge of the body, and wherein the gap forms adiscontinuity about a circumference of each shield member.
 10. Thewireless power transmitting device of claim 9, wherein each shieldmember further defines a plurality of slots extending from the innerannular edge of the body towards the outer annular edge of the body. 11.The wireless power transmitting device of claim 8, wherein each shieldmember of the one or more shield members comprises a grounding pinextending from an inner annular edge of the body and electricallycoupling the shield member with a ground of the wireless powertransmitting device.
 12. A wireless power transmitting device,comprising: a contact surface configured to support one or more wirelesspower receiving devices; an induction coil; and a shield positionedbetween the induction coil and the contact surface, wherein the shieldcomprises a shield member overlying and aligned with the induction coil.13. The wireless power transmitting device of claim 12, wherein theshield comprises a conductive chassis extending about a perimeter of theshield, and wherein the shield comprises a conductive sheet spanning aninternal area defined by the conductive chassis.
 14. The wireless powertransmitting device of claim 13, wherein the conductive sheet comprisessilver, and wherein the shield member comprises copper.
 15. The wirelesspower transmitting device of claim 13, wherein the shield comprises aplurality of shield members, and wherein each shield member iselectrically coupled with another shield member with a bridge or iselectrically coupled with the conductive chassis with a conductivedrain.
 16. A wireless power transmitting device, comprising: a contactsurface configured to support one or more wireless power receivingdevices; one or more coils; and a shield positioned between the one ormore coils and the contact surface, wherein the shield comprises: aconductive chassis, a conductive sheet extending across an internal areadefined by the conductive chassis, and a shield member positioned on theconductive sheet and overlying a coil of the one or more coils.
 17. Thewireless power transmitting device of claim 16, wherein the conductivesheet comprises a first material, wherein the shield member comprises asecond material, and wherein the conductive sheet is characterized by ahigher sheet resistance than the shield member.
 18. The wireless powertransmitting device of claim 16, wherein the shield comprises aplurality of shield members, and wherein each shield member iselectrically coupled with another shield member with a bridge or iselectrically coupled with the conductive chassis with a conductivedrain.
 19. The wireless power transmitting device of claim 18, whereineach coil of the one or more coils is characterized by a substantiallyannular shape, and wherein each shield member of the plurality of shieldmembers comprises a body characterized by a substantially annular shape.20. The wireless power transmitting device of claim 19, wherein eachshield member of the plurality of shield members defines a gap extendingfrom an inner annular edge of the body to an outer annular edge of thebody, and wherein the gap forms a discontinuity about a circumference ofeach shield member body.